A copy of "ST" should live in xc/extras/ (e.g. in xc/extras/ST/ or
xc/extras/STSF/) that the Xorg tree can be build out-of-the-box without the need
of building and installing "ST" seperately (note that FreeType2 resides under
xc/extras/freetype2/ for the same reason).
We discussed that and decided against integrating STSF into the xorg tree since
the monolithic tree will be soon replaced by the modular tree.